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  <title>Document</title>
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  <script>
    let num = 10;
    // 前置自增运算符
    console.log(++num);
    // 后置自增运算符
    console.log(num++);
    // 区别
    let i=1
    console.log(i++ + 1); // 2
    let a=1
    console.log(++a + 1); // 3
    let c=1
    console.log(c++ + ++c + c) //7
  </script>
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